Interface ExpressionVisitor

Please note that a generic visit( Expression ) entry point has not been provided, although Expression
forms a heirarchy for your convience it is not an open heirarchy. If you need to extend this system
please make use of {code Function}, this will allow extention while remaining standards complient.

It is very common for a single instnace to implement both ExpressionVisitor and FilterVisitor.

Method Detail

visit

Used to visit a Expression.NIL, also called for null where an
expression is expected.
This is particularly useful when doing data transformations, as an example when
using a StyleSymbolizer Expression.NIL can be used to represent the default
stroke color.